The Medicare Prescription Drug, Improvement and Modernization Act of 2003 (MMA), led to the Centers for Medicare & Medicaid Services (CMS) combining 43 Fiscal Intermediaries and carriers into 15 Medicare Administrative Contractors (MACs) in part to reduce variations in access to treatment. The goal of the proposed research is to perform a difference-in-differences analysis to determine the impact of the MMA legislation on the receipt of guideline- recommended colon cancer treatment among Medicare beneficiaries. This research will compare the receipt of [1] National Comprehensive Cancer Network (NCCN) recommended treatment, [2] survival, and [3] cost of care for elderly Medicare colon cancer patients with metastatic disease before and after MAC implementation in order to inform national coverage policies that will result in optimal treatment decisions for Medicare colon cancer patients. This project will be the first to comprehensively examine the impact of MAC implementation on Medicare colon cancer patients and will take advantage of the clinical and resource utilization data found in the SEER-Medicare dataset. As more than 60% of colon cancer patients are found within the Medicare population (>65 years old), the proposed research will determine the association between colon cancer treatment and MAC implementation using real-world data from the AHRQ priority population that bears the majority of the disease burden. The long term goal of this research is to improve Medicare coverage for cancer treatment in order to minimize wasteful spending and improve the quality of care and survival for Medicare colon cancer patients.